Combustors are commonly used in many forms of commercial equipment. For example, gas turbines typically include one or more combustors that mix fuel with a working fluid to generate combustion gases having a high temperature, pressure, and velocity. Many combustors include nozzles that premix the fuel with the working fluid prior to combustion. Premixing the fuel with the working fluid prior to combustion allows for leaner fuel mixtures, reduces undesirable emissions, and/or improves the overall thermodynamic efficiency of the gas turbine.
During normal combustor operations, a combustion flame exists downstream from the nozzles, typically in a combustion chamber at the exit of the nozzles. Occasionally, however, an event referred to as “flame holding” occurs in which a combustion flame exists upstream of the combustion chamber inside the nozzles. For example, conditions may exist in which a combustion flame exists near a fuel port in the nozzles or near an area of low flow in the nozzles. Nozzles are typically not designed to withstand the high temperatures created by flame holding, and flame holding may therefore cause severe damage to a nozzle in a relatively short amount of time.
Various methods are known in the art for preventing or reducing the occurrence of flame holding. For example, flame holding is more likely to occur during the use of higher reactivity fuels or during the use of higher fuel-to-working-fluid ratios. Flame holding is also more likely to occur during operations in which the fuel-working fluid mixture flows through the nozzles at lower velocities. Combustors may therefore be designed with specific safety margins for fuel reactivity, fuel-to-working-fluid ratios, and/or fuel-working fluid mixture velocity to prevent or reduce the occurrence of flame holding. While the safety margins are effective at preventing or reducing the occurrence of flame holding, they may also result in reduced operating limits, additional maintenance, reduced operating lifetimes, and/or reduced overall thermodynamic efficiency. Therefore, a nozzle, combustor, and/or method for operating the combustor to respond to flame holding would be desirable.